Actually, if NFLX pivoted their DVD-rental business (which they are planning to sell) to Digital Dowload-to-Own, there are new customers they can bring. Also, since it is a transactional business, there will be a steady income stream with every new release and people who want to own the Blu-ray equivalent digital edition.

They probably are worried about the cannibalization of the subscription base and hence caught in the Innovator's Dilemma.